I think that we have all had that problem and you are exactly right - you can't move forward with anything until everyone is comfortably off book.

I have had the problem with several actors - we are a retirement community and we do plays that appeal to an older audience and that usually means older actors. 

In one case the lead was a 65+ woman who had over half the lines in a 2 1/2 hour play (my fault!!).  She worked on her lines every spare moment and still had problems.  At some point she started taking some natural supplement (Ginko Biloba???) and it really, really helped.  I am not into  these types of supplements but it did work for her.

In another case, the problem was not lack of effort on the actors part.  She worked incredibly hard but lines that were there at lunch were gone by the evening rehearsal.  She spent 8 hours a day outside of rehearsal on her lines - I had the feeling that she was trying too hard - not getting one scene down before moving on to another and just confusing her.  I talked to a lot of people about whether I should replace her and my final decision was to stay with her (over the vocal objections of some of the other cast members).  This is community theater.  If I replaced the actor, the entire community would have been aware of it.  I cast the show and I had to live with that choice. 

We did many things to ease the problem - we let the actor make up "cheat sheets" and carry them during the play.  They were in a receipe book, family almanac, sewing kit, in drawers and so on.  We spent an incredible amount of time on Improv.  We did run through after run through with the other actors learning to fill in the gaps - they got quite good at it.  Every time she came off stage, we gave her a card with her next scene on it to refresh her.  I had a back stage person there to make sure she made her entrances and so on.  The really strange thing was that it came together just before we opened - We opened on Thursday, on the Saturday before opening she couldn't remember a line, then on Sunday, she showed up and remembered lines she forgot a month ago.  The show never got to the level it should have but we were all satisfied with the result.

I saw a (very unsatisfactory) attempt to wire an actor having trouble with lines.  They read the lines to him through an earpiece.  There was always a very long pause before the actor said his lines while they read them to him and some times he still got them wrong and they had to re-read them.

In a final case that I know of, the actor gracefully withdrew from the production.  Time was short and it was the leading role so a professional actor was brought in.

I have learned a couple of lessons:  I spend a lot of early rehearsal time on HOW to learn lines.  Different people need different methods.  I make sure that they realize that there is no "silver bullet".  Learning lines is hard work and nothing works except doing the work (unless you are a kid - then the lines just fall in place).  In an eight week rehearsal period, I used to give everyone four weeks to learn their lines then went off book.  Now, I break it up further with a short period to get the first scene off book.  Then I can spot potential problems earlier and work on them.

From your post, I think you are looking for a reason to replace the actor - if you have not already decided to do it.  You have to make your own decision but you cast this person and you need to live with the decision.

Good comments and interesting perspectives...

I (like all directors) have "Been There" .  Actors who are slow on lines cause a long list of problems including bringing down the quality of a show and increased moral problems among the cast.

Some suggestions that have worked for me:

Do a lot of table work early on in the rehearsal process...I have found that the more actors reallly understand what is happening (the plot, the themes, the relationships, the sub text, the references, the time period etc.) the better for line learning. Sit around with entire cast and read the play aloud many times. You talk , (share your vision, explain the themes you intend to pull out and your what your research has turned up anout themes, time period etc.) to them.

Set a firm schedule of off book dates...publish the rehearsal schedule with these dates included and distribute first day ...space out the deadlines by acts or pages or whatever works for script...have a final off book with no more scripts allowed (but they can call for line)...and a final day to call for line...after which they will have to "fake it" up there with no help form you or the stage manager or book holder..(EX: off book act one: Oct. 1, Off book act 2: Oct 7 ...no more scripts out Oct. 17, final off book no calling for line...Oct 21.)

These have improved the situation for my shows...hope it helpsyou.

Good luck,

Countbio

The best way to learn lines is to understand them, and to duplicate the process your brain actually uses in putting spoken words together.  Generally, that's through visual imagery.

When you tell me what you did this morning when you woke up, you're replaying the scene in your head.  So to learn your lines, you need to create and replay a visual movie in your head of what was going on in precise detail.

With practice, your word selection . . . or should I say your character's word selection . . . will match the text exactly.

 u werent much hlp sorry 2 be negative but ur advice was too complicated and i was unfortunately excused from my play because of the fact i dint no mi lines no matter how much help i had